Yeats from "A Poet to his Beloved"

Poem lyrics of A Poet To His Beloved by William Butler Yeats.

I bring you with reverent hands
The books of my numberless dreams,
White woman that passion has worn
As the tide wears the dove-grey sands,
And with heart more old than the horn
That is brimmed from the pale fire of time:
White woman with numberless dreams,
I bring you my passionate rhyme.

Passion has worn this woman. She is the object of the poet's imploring gaze. In his eyes, she is white, dreamy, and glowing on the dove-grey sands of time. This poem has wonderful imagination. I am confused about "with heart more old than the horn". Is that some kind of chalice? The good thing about poetry is that when you read it again years later, it has different meanings. Right now I think Yeats is talking about some kind of romantic chalice, but in a few years I will probably think it is a metaphor for something more meaningful.